1. Field of the Invention
The present invention relates to a storage management system for a memory card, wherein data such as image data are stored in a memory card in the form of a file, for example.
2. Description of the Prior Art
In the field of electronic still cameras, for example, a system for storing in a memory card data representative of an image captured together with management data representative of the order of storage and indication of an occupied storage area is proposed by a co-pending Japanese patent laid-open publication, No. 286077/1988, filed in the name of the same applicant as of the present application. The image data recording system thus proposed is capable of optionally erasing individual picture images and also capable of exchanging or rearranging the sequence of the picture images. In this system, however, the storage capacity of each storage area for image data is fixed. Consequently, it has been a defect of this system that the management of storage areas in terms of efficiently storing a plurality of picture images of different size is complicated.
Also, in a co-pending Japanese patent laid-open publication, No. 193236/1990, filed in the name of the same applicant as of the present application, there is proposed a memory management system capable of efficiently storing data of variable size. According to the prior art, in the memory management system, for a memory card having a storage area divided into a plurality of clusters, for managing the storage of information on each cluster, the relationship of ones of a plurality of clusters in an image field of information is stored is indicated on a memory allocation table (MAT) a cluster in which the beginning portion of the image field of information is stored is indicated on a directory.
In the prior art, the storage areas of the memory card are managed in two different kinds of storage management areas. Consequently, when such unusual operation as unloading of a memory card from a camera during recording operation is carried out, for example, logical inconsistency may occur in the management information between the two kinds of management areas. This logical inconsistency may, when subsequently using the card, cause clusters to be permanently unusable for writing data in and reading data out of those clusters. In other words, when chained information between a MAT and a directory is broken for some reasons, clusters included in the chained information will not be usable thereafter. The similar situation will occur in a case where the logical inconsistency or errors are included in the data itself on the management areas.
Further, writing of the data into the memory card is sequentially performed. Consequently, in such a situation that one block information such as an image field of information must be stored on a distribution basis in a plurality of clusters which are scattered on the storage areas of the memory card, a time required for the storage would be increased. In addition, in a case where a random access scheme is employed, the control would be complicated and thus the system would be subjected to a large load.
The term "memory card" used in this specification means not only a storage medium which has a semiconductor storage device supported by a card type of base material and is detachably connected to other equipment but also a storage medium which is detachably connected to other equipment, such as a memory cartridge and the like having a semiconductor storage device sealed in a mold package and detachably connected to other equipment.